JPH0360412B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information detection device in a so-called TTL autofocus camera that detects a focal point and automatically focuses by receiving transmitted light from an exchangeable photographic lens.

The transmitted light of the photographic lens attached to the camera body is received by the light receiving element provided on the camera body side, and the amount of the image plane between the predetermined focal plane of the photographic lens, that is, the film plane, and the actual image plane of the subject is calculated. A so-called TTL focus detection device is known, for example, from Japanese Patent Application Laid-Open No. 159259/1983, and it calculates the amount of movement of the photographing lens from the detected amount of deviation of the image plane, and detects the entire photographic lens or Focus is achieved by moving a part of the focusing lens. To simplify the explanation, we will describe a system in which all groups of the photographic lens are moved to focus as shown in Fig. 1.
Image plane deviation amount Δx between 2 and the actual object image plane 3
Assuming that the image of the subject P is aligned on the focal plane 2 by detecting this and moving the lens by a movement amount Δd corresponding to this shift amount Δx, the following relationship holds true.

1/R-D+1/D+Δx+1/f...(1) where R is the shooting distance from focal plane 2 to the subject, D is the distance between the lens position and the focal plane before correction of the amount of deviation, and f is the focal length of the lens. . In this case R
is the normal shooting distance, that is, R is the lens movement amount Δd
If it is much larger, it becomes ΔxΔd. In addition, in the case of the so-called internal focusing type in which a part of the focusing moving lens of the photographic lens is moved, the amount of movement x of the image plane and the amount of movement Δd of the lens are approximately proportional under R〓Δd. Therefore, if the proportionality constant is known, the image plane movement amount x is x≒kΔd (k is the proportionality constant)
You can know from.

One method for controlling the lens movement amount Δd corresponding to the predetermined image plane movement amount x as described above is to control the relative image plane movement amount x rather than the lens movement.
A control circuit installed in the camera body is provided with means for generating a number of electric pulses corresponding to the number of electric pulses, and the lens drive signal is Measures are taken to issue a message.

When the above-mentioned pulse generating means is installed together with a lens drive device in an interchangeable lens assembly, the power and control signals for controlling the drive device are transmitted through a contact terminal provided at the joint between the camera body and the interchangeable lens. The pulse signal has to be transmitted from the camera body side, and conversely, the pulse signal must be sent to the control circuit on the camera body side via another contact terminal. Furthermore, in order to perform automatic focus adjustment accurately, information such as focal length information, subject distance information (distance scale information), aperture value information, and other aperture value information must be exchanged in relation to the depth of focus of the photographic lens. It is sent from the lens side to the camera body side, but if you try to transmit these many pieces of information independently, you will need a means to convert each piece of information into an electrical signal,
One electrical circuit system is required each, consisting of a means for detecting the electrical signal and a connector contact for transmitting the electrical signal from the interchangeable lens to the camera body. Therefore, the configuration of the electric circuit becomes complicated and its components become unnecessarily large.
The space required for this increases, resulting in the disadvantage that the camera not only becomes larger but also costs more. Therefore, it is desirable to reduce the number of connector contacts.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide an information detection device that uses a small number of signal transmission systems to obtain information necessary for detecting a larger number of focal points than the signal transmission system. be.

In order to achieve the above object, the present invention focuses on the fact that a certain physical correlation exists between the amount of image plane movement, the focal length of the interchangeable lens, and the object distance, and uses an image plane movement amount signal. In an automatic focusing camera that controls lens drive by using a camera, the information transmission system is reduced by determining the distance information of one of the focal length information and the object distance information, and the distance information of the other from the image plane movement amount information. This is how it was done.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

FIG. 2 is a cross-sectional view for explaining an embodiment of the present invention, in which light from a subject that has passed through the photographing lens 11 of the interchangeable lens structure L is transmitted through one of the swinging mirrors 12 in the camera body B of the single-lens reflex camera. The light passes through the oscillating mirror 12, is reflected downward by a sub mirror 13 that moves together with the oscillating mirror 12, and enters the focus detection device 14. The light receiving surface of this focus detection device 14 is provided at a position conjugate with the film surface F, and corresponds to the predetermined focal plane 2 in FIG. Δx is detected by this focus detection device 14. The sign (±) of this shift amount ±Δx indicates that the image plane is located in front of the light receiving surface, and this value Δx indicates the magnitude of the shift. On the other hand, the light reflected upward by the swinging mirror 12 is directed toward the focus plate 15 and
The image formed is observed through the pentalism 16 and the eyepiece 17.

The output of focus detection device 14 is sent to control circuit 18 . This control circuit 18 controls the interchangeable lens structure L based on the output of the focus detection device 14 corresponding to ±Δx.
The reversible motor 19 generates a drive signal that causes the reversible motor 19 inside to rotate forward, reverse, or suddenly stop.
In response to a drive signal from the control circuit 18, a movable lens barrel 21 that holds the photographing lens 11 is rotated via a gear interlocking mechanism 20. This moving lens section 21 is
Since it is screwed to the interchangeable lens structure L by a lead screw 21a, it rotates in accordance with the rotation direction of the reversible motor 19 and moves back and forth along the optical axis, until the photographing lens 11 reaches the in-focus position. When to stop. The motor 16, the gear interlocking mechanism 20, the movable lens barrel 21, and the lead screw 21a constitute a focusing lens driving means.

Image plane movement amount signal generating means 22 and 23 are provided adjacent to the gear interlocking mechanism 20 and will be described in detail later.
Based on the rotational speed of the reversible motor 19 or the amount of movement of the photographing lens 11, outputs an image plane movement amount signal representing the amount of movement of the imaging plane accompanying lens movement. This image plane movement amount signal is transmitted from the interchangeable lens assembly L to the camera body B and input to the control device 18. When this image plane movement amount signal reaches a value corresponding to the magnitude of the focus detection signal, the motor drive is abruptly stopped. In this way, the photographing lens 11 is driven so that the image plane moves by the same amount as the image plane shift amount Δx detected by the focus detection device 14.

FIG. 3 shows a specific configuration of the image plane movement amount signal generating means 22 and 23 for obtaining an image plane movement amount signal, and shows the specific configuration of the image plane movement amount signal generating means 22 and 23 for obtaining the image plane movement amount signal.
4 is provided with connector contacts P ₁ to P ₅ for transmitting and receiving signals with the camera body B side, and the reversible motor 19 is connected to the control device 18 on the camera body B side via these contacts P ₁ and P ₂ . It is formed to receive the drive output of. The rotation of this reversible motor 19 is controlled by the reduction gears 20A, 20B, 2 of the gear interlocking mechanism 20.
The signal is transmitted to a reduction gear 20D with a wide tooth width provided on the movable lens barrel 21 via 0C. This rotation of the final stage reduction gear 20D is converted into a movement in the optical axis direction by the lead screw 21a, and the photographing lens 11
move in the direction of the optical axis. Further, an image plane movement amount detection pattern 23 is provided on the end surface of the intermediate gear 20B. This pattern 23 includes a high reflection part 23a with a high light reflectance and a low reflection part 23b with a low reflectance.
It is formed by dividing a circle into four equal parts. light source 2
2A projects light onto a specific portion of the pattern 23, and the reflected light is received by the light receiving device 22B.
This light receiving device 22B generates two pulses per rotation in accordance with the rotation of the pattern 23 accompanying the rotation of the intermediate gear 20B. This pulse output is
The connector contact is used as an image plane movement amount signal that indicates the amount of movement of the image plane that moves in response to the amount of movement of the lens.
The signal is sent to the control device 18 in the camera body B through _P3 . The above pattern 23, light source 22A, and light receiving device 22B constitute image plane movement amount signal generating means.

FIG. 4 shows a specific configuration example of an electric circuit for obtaining the above-mentioned pulse output. In the interchangeable lens structure L, a light emitting diode 22A' as a light source 22A is connected to a power source via a resistor _R1 , A phototransistor 22B' is provided as the light receiving device 22B, and its emitter is grounded and its collector is connected to the connector contact _P3 . On the camera body B side, a contact P ₃ ' that contacts the contact P ₃ is connected to the power source via a resistor R ₂ , and this connector P ₃ ' enters one input terminal of the comparator 25 . A constant voltage source 26 is connected to the other input terminal of the comparator 25 as a reference voltage. With the above configuration, the light intermittently reflected by the image plane movement amount detection pattern 23 that rotates with the movement of the photographing lens 11 is transmitted to the phototransistor 22 of the light receiving device 22B.
A collector current flows intermittently due to the voltage applied from the camera body B side by turning B' on and off, and the voltage appearing at the collector, that is, the contact P ₃ or P ₃ ' becomes a rectangular pulse. By comparing this signal using an appropriate constant voltage source 26 as a reference, a number of waveform-shaped pulse outputs proportional to the relative image plane movement amount x can be obtained as the output of the comparator 25.

Now, the distance D between the focusing lens 1 and the focal plane 2 in the above equation (1) is made equal to the focal length of the focusing lens 1, that is, the focusing lens 1 is set so as to focus at infinity. As shown in Fig. 7, if the amount of deviation of the imaging plane of the subject P, that is, the absolute amount of image plane deviation, is △X, based on this infinity focus, then D can be expressed in equation (1). By substituting =f△x=△X, the following equation is obtained.

R=f ² /ΔX+2f... (2) If the above equation (2) is used, only one piece of information, for example focal length information, can be exchanged using the image plane movement amount signal output from the comparator 25 mentioned above. By simply transmitting the information from the lens L to the camera body side, the subject distance can be calculated and determined on the camera body side, eliminating the need to obtain this subject distance information from the interchangeable lens side. However, the image plane movement amount signal obtained in the above embodiment is a relative one that changes depending on the distance between the focusing lens and the predetermined focal plane, that is, D in equation (1), and (2) What is required in the formula is the absolute image plane movement amount X corresponding to the image plane shift amount ΔX with reference to the infinity focusing state. Therefore, (2) can be used as is in an automatic focusing camera in which the focusing lens is always driven to focus starting from the infinity focusing position. However, since the relative image plane shift amount is generally detected as shown in Figure 1, the fourth
A conversion means is required to convert the relative image plane movement amount obtained in the illustrated embodiment into the above-mentioned absolute value image plane movement amount.

FIG. 5 shows a specific example that includes this conversion means and calculates the object distance on the camera body B side using the image plane movement amount signal and the focal length information.
The pulse of the relative image plane movement amount signal output from the comparator 25 is sent to the lens drive control circuit 18 and is also input to the up-down counter 27. The up-down selection terminal of this up-down counter 27 receives a drive direction signal from the control circuit 18, and the reset terminal Re of the up-down counter 27 receives a drive direction signal from the control circuit 18.
An infinity signal is received from This infinity signal is transmitted to the contact P ₄ on the interchangeable lens L side, the switch SW ₁ connected between the contact P ₄ and the ground, and the switch SW 1 connected between the contact P ₄ ' on the camera body B side and the power source. is generated by a circuit consisting of a resistor _R3 and an interchangeable lens structure L.
The switch SW 1 is configured to close only when the distance ring 28 (see FIG. 2) is at the infinity position, that is, when the photographing lens ₁₁ is at the infinity focusing position. The output of the up-down counter 27 passes through the conversion means 29 and enters one input of the calculation means 30. On the other hand, the resistor _R4 in the interchangeable lens structure L is a fixed resistor that maintains a certain relationship between the resistance value and focal length f of the interchangeable lens to be attached (however, in the case of a zoom lens, it is a variable resistor). )
One end is grounded and the other end is connected to contact _P5 .
A constant current source 31 is connected to the contact P ₅ ′ on the camera body side that comes into contact with the contact P ₅ , and a replacement means 32
to go into. The output of this conversion means 32 is also
enter other inputs.

Since the circuit shown in FIG. 5 is configured as described above, the relative image plane movement amount signal pulse output from the comparator 25 is used in the up-down counter 27 to set the infinity position of the photographing lens to 0 (zero). The direction, that is, the sign of ± is counted, and the output is a digital output with a value proportional to the absolute image plane movement amount. On the other hand, when the current from the constant current source 31 flows through the resistor R ₄ via the contacts P ₅ and P ₅ ',
A voltage proportional to the resistance value of the resistor R ₄ is generated at the contact P ₅ ′. Therefore, this voltage has a certain relationship with the focal length of the attached photographic lens. Therefore, the output of the up-down counter representing the amount of image plane movement and the voltage of the contact P ₅ ' representing the focal length are converted into appropriate forms by the converting means 29 and 32, respectively, and the respective values X and By using f, the arithmetic means 30 calculates the above-mentioned equation (2), and the object distance information R can be obtained from the output of the arithmetic means 30.

Next, _the contacts P ₅ and P ₅ ' for transmitting focal length information in _the embodiment shown in FIG. An example is shown in FIG.

In FIG. 6, in the interchangeable lens structure L, the contact P ₃ is connected to the collector of the phototransistor 22B' of the light receiving device 22B, as well as a resistor having a resistance value r that has a certain relationship with the focal length f of the photographing lens 11.
R ₄ ′ is connected. In addition, on the camera body B side, a constant current source 3 outputs a current of current value i to the contact P ₃ '.
Voltage sensing means 33 is connected between P 1 ′ and ground, and contact P ₃ ′ enters one input of comparator 25 . A constant voltage source 26 is connected to the other input of the comparator 25. The output of the voltage detection means 33 enters the conversion means 32. Other parts are the same as the embodiment shown in FIG.

With the above configuration, the light that is intermittently reflected by the detection pattern 23 that rotates with the movement of the photographic lens 11 is transmitted to the phototransistor 22.
B' is turned on and off, and the constant current i from the constant current source 31' on the camera body B side is applied to the phototransistor 2.
2B′ and resistor R ₄ ′ alternately, and the contactor P ₃ or
The voltage appearing at P ₃ ' becomes a rectangular wave pulse.
The voltage of this pulse is
When B' is on, it is at a low level (voltage is approximately 0), and when it is off, it is at a high level (voltage V=i·r). By comparing this signal with a suitable constant voltage source 26 lower than V as a reference, the output of the comparator 25 provides a number of waveform-shaped pulse outputs proportional to the relative amount of image plane movement. . Here, the voltage V appearing at the contact P ₃ when the phototransistor 22B' is off is proportional to the resistance value r of the resistor R ₄ '. Since this resistance value r is set to have a certain relationship with the focal length f of the photographing lens 11, this voltage V
also has a certain relationship with the focal length f of the photographic lens 11. Therefore, by the voltage detection means 33,
By detecting the voltage when the phototransistor 22B' is off, focal length information can be obtained by using the contact between the interchangeable lens structure L and the camera body B as the contact for transmitting the image plane movement amount signal. It becomes possible.
The operation of determining the object distance using the image plane movement amount signal pulse and the output of the voltage detection means 33 representing the focal length of the photographic lens is the same as in the embodiment shown in FIG.

In the two embodiments shown in FIGS. 5 and 6 above, the focal length information is detected and the object distance is determined through calculation processing. The case where the focal length is calculated by detecting the object distance information based on the position of the object can be realized by the completely similar embodiment. In this case, the above equation (2) can be transformed as follows.

f=-ΔX+√(+) ...(3) Then, if the resistance values of R ₄ in FIG. 5 and R ₄ ' in FIG. Thus, the focal length f of the photographic lens can be obtained.

Note that in the above embodiment, the image plane movement amount x or
As described above, focus adjustment is performed on the condition that the amount of lens movement Δd or d is approximately equal or in a proportional relationship, but due to lens design considerations, in the case of internal focusing type focusing, the amount of image plane movement and In the case where a proportional relationship does not hold between the amounts of lens movement, for example, the gear 20 in FIG.
The pattern 23 is rotated in conjunction with the movement of the lens D, and a correction cam or the like is provided in the interlocking mechanism to calculate the rotation speed of the pattern 23 representing the amount of lens movement and the amount of image plane movement corresponding to the amount of lens movement. It may be corrected so that they have a linear relationship.

As is clear from the above description, according to the present invention, in a camera that performs focusing control using an image plane movement amount signal, an interchangeable lens that is required for purposes other than focusing, such as display in the viewfinder, can be used. In order to detect two types of information, focal length information and subject distance information, on the camera body side, if only one of the two types of information is transmitted from the interchangeable lens side to the camera body side, the other information can be detected. Since this is calculated and determined on the camera body side, the information transmission system becomes simpler, and both the interchangeable lens and the camera body can be made smaller, lighter, and lower in cost.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the relationship between the photographic lens and the imaging plane, Fig. 2 is a sectional view of an embodiment of the present invention, and Fig. 3 is a perspective view showing the internal structure of the interchangeable lens side of the embodiment of Fig. 2. 4 is a diagram of an image plane movement amount signal generation circuit used in an embodiment of the present invention, FIGS. 5 and 6 are block diagrams showing different embodiments of the present invention, and FIG. 7 is a diagram of an absolute image FIG. 3 is an optical system layout diagram for explaining the amount of surface movement. 14... Focus detection means, 18... Control means, 1
9, 20, 21... Focusing lens driving means, 2
2, 22A, 22A', 22B, 22B', 23,
25, 27, R ₂ , R ₃ , SW ₁ ... image plane movement amount signal generator, R ₄ ... distance information means, 30 ... calculation means, 31 ... constant current source.

Claims (1)

[Claims] 1. A device provided in the interchangeable lens body according to the detection output of a focus detection means, which is provided on the camera body side and detects the amount of deviation between a predetermined focal plane and the imaging plane of the subject by receiving the transmitted light of the interchangeable lens. In an automatic focusing camera that automatically adjusts focus by driving a focusing lens drive means, the amount of lens movement corresponds to the amount of deviation between the focal plane for an infinite distance and the imaging plane for the subject to be focused on. image plane movement amount signal supply means for supplying a signal representing the image plane movement amount corresponding to; distance information input means for inputting distance information of either the focal length of the interchangeable lens or the object distance from the interchangeable lens; an automatic focusing camera characterized by comprising: a calculating means for receiving signals from the image plane movement amount signal supplying means and the distance information inputting means and calculating distance information of the other one.